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SLSH

Section: (1)
Updated: 06 May 2006
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NAME

slsh - Interpreter for S-Lang scripts  

SYNOPSIS

slsh [ --help ] [ --version ] [ -g ] [ -n ] [ --init file ] [ --no-readline ] [ -i ] [ -t ] [ -v ] [ -|script-file args... ]

 

DESCRIPTION

slsh is a simple program for interpreting S-Lang scripts. It supports dynamic loading of S-Lang modules and includes a readline interface for interactive use.  

OPTIONS

--help
Show a summary of options
--version
Show slsh version information
-g
Compile with debugging code, tracebacks, etc
-n
Don't load the personal initialization file
--init file
Use this file instead of ~/.slshrc
--no-readline
Do not use a readline interface for the interactive mode
-i
Force interactive mode. Normally slsh will go into interactive mode if both stdin and stdout are attached to a terminal.
-t
Normally, slsh will call slsh_main if it is defined. This option prevents that from happening making it useful for checking for syntax error.
-v
Show verbose loading messages. This is useful for seeing what files are being loaded.
 

INITIALIZATION

Upon startup, the program will try to load slsh.rc as follows. If either SLSH_CONF_DIR or SLSH_LIB_DIR environment variables exist, then slsh will look look in the corresponding directories for slsh.rc. Otherwise it will look in:

$(prefix)/etc/ (as specified in the Makefile)

/usr/local/etc/

/usr/local/etc/slsh/

/etc/

/etc/slsh/

The slsh.rc file may load other files from slsh's library directory in the manner described below.

Once slsh.rc has been loaded, slsh will load $HOME/.slshrc if present. Finally, it will load the script specified on the command line. If the name of the script is -, then it will be read from stdin. If the script name is not present, slsh will go into interactive mode and read input from the terminal. If the script is present and defines a function called slsh_main, that function will be called.  

LOADING FILES

When a script loads a file via the built-in evalfile function or the require function (autoloaded by slsh.rc), the file is searched for along the SLSH_PATH as specified in the Makefile. An alternate path may be specified by the SLSH_PATH environment variable.

The search path may be queried and set during run time via the get_slang_load_path and set_slang_load_path functions, e.g.,

   set_slang_load_path ("/home/bill/lib/slsh:/usr/share/slsh");
 

INTERACTIVE MODE

When slsh is invoked without a script or is given the -i command line argument, it will go into into interactive mode. In this mode, the user will be prompted for input. The program will leave this mode and exit if it sees an EOF (Ctrl-D) or the user exits by issuing the quit command.

If an uncaught exception occurs during execution of a command, the error message will be shown and the user will be prompted for more input.

Any objects left on the stack after a command will be printed and the stack cleared. This makes interactive mode useful as a calculator, e.g.,

     slsh> 3*10;
     30
     slsh> x = [1:20];
     slsh> sum (sin(x)-cos(x));
     0.458613
     slsh> quit;
Note that in this mode, variables are automatically declared.

The interactive mode also supports command logging. Logging is enabled by the start_log function. The stop_log function will turn off logging. The default file where logging information will be written is slsh.log. An alternative may be specified as an optional argument to the start_log function:

     slsh> start_log;
     Logging input to slsh.log
        .
        .
     slsh> stop_log;
     slsh> start_log("foo.log");
     Logging input to foo.log
        .
        .
     slsh> stop_log;
     slsh> start_log;
     Logging input to foo.log

Similarly, the save_input function may be used to save the previous input to a specified file:

     slsh> save_input;
     Input saved to slsh.log
     slsh> save_input ("foo.log");
     Input saved to foo.log

As the above examples indicate, lines must end in a semicolon. This is a basic feature of the language and permits commands to span multiple lines, e.g.,

     slsh> x = [
            1,2,3,
            4,5,6];
     slsh> sum(x);
For convenience some users prefer that commands be automatically terminated with a semicolon. To have a semicolon silently appended to the end of an input line, put the following in $HOME/.slshrc file:

    #ifdef __INTERACTIVE__
    slsh_append_semicolon (1);
    #endif

The interactive mode also supports shell escapes. To pass a command to the shell, prefix it with !, e.g.,

    slsh> !pwd
    /grandpa/d1/src/slang2/slsh
    slsh> !cd doc/tm
    slsh> !pwd
    /grandpa/d1/src/slang2/slsh/doc/tm

Finally, the interactive mode supports a help and apropos function:

    slsh> apropos list
    apropos list ==>
    List_Type
    list_append
    list_delete
       .
       .
    slsh> help list_append
    list_append

     SYNOPSIS
       Append an object to a list

     USAGE
       list_append (List_Type, object, Int_Type nth)
       .
       .
For convenience, the help and apropos functions do not require the syntactic constraints of the other functions.  

MISCELLANEOUS SCRIPTS

Several useful example scripts are located in $prefix/share/slsh/scripts/, where $prefix represents the slsh installation prefix (/usr, /usr/local,...). These scripts include:

sldb
A script that runs the S-Lang debugger.
jpegsize
Reports the size of a jpeg file.
svnsh
A shell for browsing an SVN repository.
 

AUTHOR

The principal author of slsh is John E. Davis <jed@jedsoft.org>. The interactive mode was provided by Mike Noble <mnoble@space.mit.edu>. The S-Lang library upon which slsh is based is primarily the work of John E. Davis with help from many others.

This manual page was originally written by Rafael Laboissiere <rafael@debian.org> for the Debian system (but may be used by others).

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 any later version published by the Free Software Foundation.

On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
INITIALIZATION
LOADING FILES
INTERACTIVE MODE
MISCELLANEOUS SCRIPTS
AUTHOR




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